A former Arkane developer provided ValveTime.net with the images, lifted from the game Arkane was making 2006/2007 before it was cancelled.

ValveTime.net, which popped the images in a video, below, noticed one HUD element it couldn't explain: "Absorption." Best guesses on a post card.

This isn't the first time we've heard of Arkane's Half-Life effort. A year ago Valve's Marc Laidlaw explained why it was cancelled to LambdaGeneration:

"We are big fans of Arkane and wanted to come up with a project we could work on together. We threw ideas around, they built some cool stuff, but we eventually decided that it didn't make sense to pursue it at the time. As I recall, we felt like a lot of the staples of Ravenholm - headcrabs and zombies! - were pretty much played out, and the fact that it would have to take place sometime before the end of Episode 2 (so as not to advance beyond where Valve had pushed the story) was a creative constraint that would hamper the project...and Arkane."